This invention relates to terminal boxes and more particularly to terminal boxes which mount directly on the curved surface of a cylindrical shell of an electric motor.
Electric motors, particularly higher horsepower electrical motors of the type used to power industrial machinery, have terminal boxes which house the connections between lead wires from the motor and feed wires from a source of electricity. The feed wires are run through a conduit into the terminal box. This conduit is attached to the terminal box by a conduit fitting. In many cases, the sidewalls of the terminal box have conduit fitting openings in which a conduit fitting can be fastened. To facilitate motor installation, it is important to be able to run the conduit to the terminal box from different directions and attach it to the side of the terminal box that it approaches. In the case of a rectangular terminal box, it is desirable to be able to run the conduit to the terminal box from any of its four sides and attach it to the side of the terminal box that it approaches. This is sometimes termed 90.degree. access.
It is also desirable that the conduit fitting opening in the sidewall of the terminal box through which the feed wires are pulled be relatively unobstructed by an opposed sidewall when the terminal box cover is open. This facilitates pulling the feed wires through the terminal box out of the conduit and conduit fitting opening of the terminal box to which the conduit is attached. A fishtape is typically used to pull wire through a conduit. The wire to be pulled is attached at one end to the fishtape. The fishtape is inserted into one end of the conduit and forced therethrough until it exits the other end of the conduit. The fishtape is then pulled to pull the wire through the conduit. Consequently, if the fishtape can be pulled from the conduit in a relatively straight line without unduly bending it, pulling wire through the conduit is made easier. If the fishtape must be bent as it exits the conduit, a more complex motion must be used to pull it as it must BEND as it exits the conduit and pulled at the same time. The terms "pulling wire", "wire pull," and the like are used herein as a short and convenient way of referring to the above process.
It is also important that an electrician who is connecting the feed wires to the motor lead wires have free access to the interior of the terminal box. This facilitates connecting the feed wires to the motor lead wires and positioning the connected wires in the terminal box.
In the past, the objectives of 90.degree. access, an unobstructed conduit opening, and free access to the interior of the terminal box have been achieved by a split terminal box. Referring to FIG. 1, a prior split terminal box assembly 10 is shown. The terminal box assembly 10 has a split terminal box 12 and an adapter 14 to mount the terminal box 12 on a cylindrical shell or housing 9 of a motor 8 as described below.
The terminal box 12 comprises a cover 18 and a base 16. The base 16 has a square bottom 20, with a front edge 22, and three sidewalls 26, 32, 34. The bottom 20 has a hole 24 extending therethrough. Lead wires (not shown) of the motor 8 are passed into terminal box 12 through the hole 24.
The sidewall 26, which is rectangular, extends vertically upwards from a back edge 23 of the bottom 20. The rectangular sidewall 26 has a hole 30 positioned approximately in the center thereof. The hole 30 is configured to receive a conventional conduit fitting (not shown).
The sidewalls 32, 34, which are triangular, extend vertically upwardly from opposite side edges of the bottom 20 of the base 16 of the terminal box 12. Top edges 36, 38 of the opposed triangular sidewalls 32, 34, respectively, extend downwardly from a top edge 28 of the rectangular sidewall 26 to the front edge 22. The sidewalls 32, 34 are mirror images of each other.
The cover 18 is essentially the mirror image of the base 16 except that it is typically not provided with the hole 30 or the like for receiving conduit fittings. The cover 18 is secured to the base 16 by screws (not shown) or other conventional fasteners. A gasket (not shown) is usually disposed between the cover 18 and the base 16 to prevent liquids such as water or oil from getting into the terminal box 12.
The terminal box 12 is a split terminal box. The joint between the base 16 and the cover 18 forms a rectangle 47 which is defined by the junction of the front edge 22 and the top edges 28, 36, 38 of the sidewalls 26, 32, 34, of the base 16, with corresponding edges 22', 28', 36', 38' of the cover 18. The rectangle 47 defines a plane which bisects the terminal box 12 from the top edge 28 of the rectangular sidewall 26 of the base 16 to the front edge 22 of the bottom 20 of the base 16. The plane defined by the rectangle 47 is vertically perpendicular to the triangular sidewalls 32, 34. That is, a transverse axis 48 of the rectangle 47 which extends through rectangle 47 along a line parallel to the top edge 28 of sidewall 26 and the front edge 22 of the bottom 20 is perpendicular to vertical axes 45, 46 of the sidewalls 32, 34.
The adapter 14 is required to mount the terminal box 12 to the curved surface of the cylindrical shell 9. The adapter 14 has a curved bottom surface 40 and a flat top surface 42. A hole 44 positioned in the top surface 42 of the adapter 14 matches with the hole 24 in the base 16 when the base 16 is positioned on the adapter 14. The terminal box 12 is secured to the flat top surface 42 of the adapter 14 by screws or other conventional fasteners.
Illustratively, as shown, the terminal box 12 can be rotated 360.degree. in 90.degree. increments on adapter 14. Consequently, the hole 30 in the rectangular sidewall 26 of the base 16 of the terminal box 12 can be positioned to permit a conduit (not shown) to be run to terminal box 12 from any one of four directions 90.degree. apart. This facilitates installation of the motor 8.
The split construction of the terminal box 12 permits easy access to the interior of the terminal box 12 and an unobstructed wire pulling path from hole 30 through the terminal box 12. When the cover 18 is removed from the base 16, the rectangular sidewall 26 of the base 16 is unobstructed by an opposed sidewall. Consequently, when an electrician is pulling the feed wires through the conduit affixed to the terminal box 12 at the hole 30 in rectangular sidewall 26, the electrician can pull the feed wires straight out of the conduit through the hole 30 without having to change the path of the wire pull. Also, since one side of the terminal box 12 is unobstructed by a sidewall, connecting the feed wires with the motor lead wires in the terminal box 12 is facilitated.
A problem with the type of terminal box such as the terminal box 12 is that the adapter 14 must be used to mount the terminal box 12 on the motor 8. This is because the bottom 20 of the base 16 of the terminal box 12 is flat to permit the terminal box 12 to be rotated 360.degree. as described above. If the bottom 20 of the base 16 was curved, it could only be rotated 180.degree. between two positions on the curved surface of the cylindrical shell 9. Consequently, a conduit could be run to the terminal box 12 in only two directions which are 180.degree. apart. If a hole was provided in one of the triangular sidewalls 32, 34 to achieve 90.degree. access, it would obstructed by the other opposed sidewall 32, 34, which would obstruct the wire pulling path.
The requirement that an adapter, for example adapter 14, be used not only adds the cost of an extra part, but it also raises the height that the terminal box 12 extends from the surface of cylindrical shell 9 of the motor 8. Since it is often desirable to minimize the height which a terminal box extends from the surface of the cylindrical shell of the motor, rectangular terminal boxes having a flat top and a curved base are often used in lieu of the above-described split terminal box because they can be mounted directly on the motor's curved surface. However, such rectangular terminal boxes, particularly those which are relatively small as are used with motors of the size typically used to power industrial equipment, do not provide an unobstructed wire pulling path. The holes which receive conduit fittings are usually positioned in the sidewalls of such rectangular terminal boxes. These holes are obstructed by opposed sidewalls. When wire or the fishtape to which the wire is attached is pulled through such a rectangular terminal box from the hole to which a conduit is attached, it must be angled upwardly to avoid the opposed sidewall. This makes it more difficult to pull wire through the conduit and the terminal box in that a more complex motion must be used to both angle and pull the wire at the same time. Also, access to such a terminal box is more restricted than the split terminal box in that access to the rectangular box is through its top.
Accordingly, there is a need for a terminal box for electric motors which can be mounted directly on the cylindrical shell of the motor without an adapter, provides 90.degree. access to the terminal box, provides a relatively unobstructed path for pulling wire through the terminal box from the conduit attached to the terminal box, and provides free access to the interior of the terminal box.
It is an object of this invention to provide a terminal box which mounts directly on the curved surface of the cylindrical shell or housing of a motor, provides 90.degree. access to the terminal box, provides a relatively unobstructed path for pulling wire through the terminal box from a conduit fitting opening in the terminal box, and provides free access to the interior of the terminal box when its cover is removed.
It is another object of this invention to provide a terminal box meeting the above-stated objective which can be manufactured using a relatively simple forming operation.
In carrying out the present invention in preferred forms thereof, I provide an improved terminal box comprising a base and a cover, each having four sidewalls. The base has a curved bottom which conforms to the curve of a cylindrical shell of an electric motor. The base has first and second conduit receiving means which are at angles to each other. The base can be rotated 180.degree. between two positions on the motor housing. A conduit can thus be run to the terminal box from any of four directions. The base is formed such that the first and second conduit receiving means are relatively unobstructed when the cover is off. This permits wire to be pulled from the conduit, which is attached to one of the conduit receiving means, through the terminal box in a relatively unobstructed path. That is, the path of the wire pull need not be angled to avoid an obstructing sidewall.
In one illustrated embodiment, the base has first and second adjacent sidewalls opposed by third and fourth sidewalls, respectively. The first and second sidewalls are relatively higher than their opposed third and fourth sidewalls, respectively. The first sidewall thus has a portion which is relatively unobstructed by the third sidewall which opposes it and the second sidewall has a portion which is relatively unobstructed by the fourth sidewall which opposes it. A conduit receiving means is formed in each of the first and second sidewalls.
In a second illustrated embodiment, the first, second, third and fourth sidewalls of the base have top edges which define a plane which is not vertically perpendicular to any of the four sidewalls of the base. By having the four top edges of the base define a plane, the base structure becomes relatively simple to form such as by stamping from a piece of flat metal stock in a single operation without the need for a pre-forming operation. The cover illustratively corresponds to the base but without the conduit receiving means. The cover thus can also be manufactured using the same type of simple forming operation.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.